Stoker



F. R. NELSON Sept. 3, 1935.

STOKER 3 Sheets-Sheet 1 Original Filed April 18, 1931 Patented Sept. 3,1935 Z,dl3,248

PATENT GFFECE STOKIER Floyd R. Nelson, Rockford, 111., assignor to GottaTransmission Corporation, Rockford, 111., a corporation of Illinois 9Claims.

This invention relates to stokers, and has for its principal object theprovision of an overload release mechanism arranged in the event ofexcessive resistance to the turning of the stoker feed screw to operatea switch and break the circuit of the electric motor, besidesdisconnecting the screw from the transmission.

Another object consists in the provision of an alarm electricallyconnected with the motor and switch in such a way as to be thrown intooperation automatically when the motor circuit is opened at the switchdue to an overload.

The invention further contemplates the provision of a thermal relay inseries with the aforesaid switch arranged tobreak the circuit in theevent of an overload in the motor itself such as would be caused, forexample, by failure to keep the motor properly lubricated. The alarmwould also be operated automatically in the eventof the motor circuitbeing broken in this way.

This application is a division of my application, Serial No. 531,100,filed April 18, 193-1, and is in part a continuation of saidapplication.

In the accompanying drawings illustrating the invention- Figure 1 is aplan view of the drive end of a stoker embodying my invention;

Fig. 2 is a horizontal section through the transmission showing theoverload release mechanism and its connection with the switchcontrolling the motor circuit;

Fig. 3 is a similar View showing the parts in released position;

Figs. 4 and 5 are sectional details on the correspondingly numberedlines of Fig. 2, and

Fig. 6 is a wiring diagram.

-The same reference numerals are applied to corresponding partsthroughout the views.

The invention is herein illustrated as applied to a stoker of theunder-feed type utilizing a feed screw, but it will soon be evident thatthe invention is adaptable for use with other stoke-rs and for thatmatter any machine on which similar features are desirable. Referring toFig- 45 ure 1, the numeral l! is applied toa'portion of the hopper fromwhich the coal is fed by the screw !2 through a suitable conduitextending forwardly from the hopper to a point under thewgrates of thefurnace, hot water heater, or boiler. Air to support combustion is alsodelivered to the furnace through an air duct l3 extending forwardly fromthe blower M. The rotor of the blower is operated by a shaft at aconstant speed, so that a shutter l6 has to be provided for the airinlet to regulate the delivery of air according to the fuel delivery. Aconstant speed electric motor ll furnishes the power for driving thescrew l2 and blower M, and is hingedly mounted on the base of the hopperI I, as shown at 58, above the housing 19 of the transmission. A spring(not shown) acts against the top of the housing I9 to raise the motor Hto keep the belt 22 under proper tension. The shaft l5 previouslyreferred to extends through suitable bearings in the housing 19 and hasa pulley 20 on the projecting end thereof directly below the pulley 2!provided on the armature shaft of the motor l'i, and the belt 22provides a driving connection between these pulleys. This accounts forthe constant speed drive of the blower. A worm (not shown) is providedon the shaft 15 in the housing is and meshes with a worm gear 25 in thehousing to provide a reduction driving connection between the motor andthe transmission.

The transmission is constructed to provide further reductions in speedto give three different constant speeds of operation of the screw i2.The housing l9 of the transmission is suitably supported from the baseof hopper l I on a large collar 26 which extends rearwardly from thebottom of the hopper l I to the housing to enclose the rear end of thescrew l2 and its coupling connection with the transmission. As shown inFig. 2, the output or driven shaft 21 of the transmission is connectedwith the rear end of the screw l2 by means of a sleeve 28 which fitsover the squared projecting end of the shaft 2i and is connected bymeans of a pin 29 to a square stub shaft 30 arranged to be received in asquare socket 3i provided in the end of the screw. The shaft 21 ismounted in anti-friction bearings 32 and 33 in the opposite ends of thehousing 19 and has the worm gear 24 mounted thereon by means of a rollerbearing 3 A pinion 35, which is keyed to the worm gear 24, meshes with agear rotatably mounted on a countershaft 31! disposed in parallelrelation to the shaft 27 and supported, as will soon appear, onanti-friction bearings 38 and 39 in the opposite ends of the housing Hi.t is obvious that the gear 36 is driven at a much lower speed thanthegear 24 by reason of the reduction drive shown. The gear '36 isarranged to be clutched to the shaft 37 for the high speed drive. Theintermediate and low speed drives are provided, respectively, by meansof two other gears it and 4H rotatably mounted on the shaft 37. The gearMI is driven in this way: a pinion 42 is keyed to the gear '36 anddrivesa gear '33 mounted as by means of roller bearings 44 on the shaft 21',and a gear is keyed to the gear 43 and meshes with the gear 40.Obviously, the gear til turns at a much slower speed than the gear 36 byreason of the reduction drive therebetween. There is a still furtherreduction between the gears 36 and 4! by reason of the fact that apinion 36, smaller than the gear 45 previously mentioned and also keyedto the gear 53, meshes with the gear fill. Reference may be made to theparent application for an explanation as to how the gears 36, 49, and iiare arranged to be individually clutched to the shaft 37 to provide thehigh, intermediate, and low speed drives, re-' spectively. It will beobserved that a pinion 41 is received on the front end of the shaft 3?in abutment with a shoulder 48 thereon and has a reduced hub portion isreceived in the bearing 38 to provide support for the front end of theshaft 3? in said bearing. The pinion 47 is normally fixed to the end ofthe shaft 37 by means of an overload release mechanism, indicatedgenerally by the numeral 5f! which is hereinafter described in detail.The pinion 4? meshes with a gear 5| keyed on the front end of the outputor driven shaft 2? whereby to transmit drive to the screw [2 at afurther reduction in speed.

The overload release mechanism 50 is clearly illustrated in Figs. 2-5and, as indicated above, provides a releasable driving connectionbetween the shaft and pinion il, the release being contingent uponexcessive'resistance to turning of the screw i2. Such excessiveresistance may result from any one of several causes, and in the case ofa stoker, the most common cause is a jam resulting from a railway spikeor large stone in the coal which upon arrival at the bottom of thehopper gets stuck and prevents turning of the screw. The mechanism 59 isfurthermore arranged as we shall see to break the motor circuit at thesame time that the drive for the feed screw is discon nected. A shearpin 85, as best appears in Fig. 5, is entered through registering slots86 and 8? provided in the hub 69 and shaft 37, respectively, and

i is held in place by a split ring 88 entered with spring action in anannular groove provided in the hub 49, the ring having engagementwiththe opposite ends of the pin as shown. The crosssection of the shearpin is such that anything beyond a predetermined resistance to turningof the screw 5 2 will result in the ends of the pin shearing off andallowing the shaft 3? to turn relative to the hub 49 of the pinion 4?.The shear pin is at the remote end of. the reduction gearing withrespect to the electric motor I i so that when a jam occurs the motor,due to the reduction drive, will readily shear the pin and there will beno danger of the motor burning out. So much for the matter of how thescrew I2 is disconnected from the transmission in the event of anoverload. Registering V-shaped notches 89 and 90 are pro vided in theend of the hub 49 and shaft 37, respectively, as best appears in Fig. 4.A plate 9| is normally disposed in abutment with the end of these parts,as shown in Fig. 2, with the diametrically extending V-shaped projection92 fitting snugly in the registering notches 89 and 90. A cap 93detachably secured to the front end of the housing i 9 and enclosing themechanism 50, has a stud 94 slidably received in a hole at the centerthereof and threaded into the center of the plate '9! to provide amounting for the plate on the cap.

when the pin 85 shears off and the shaft 37 turns.

with respect to the hub 49 the plate 9| is cammed away from the shaft37, as shown in Fig. 3, by reason of the turning of the notch so withrespect to the projection 92. This movement of the plate SI is utilizedto break the motor circuit by having the stud ii move a trigger $5 of aswitch 9?. Any suitable form of switch may be used but I prefer using alimit switch similar to those used on elevators and the like and alsoquite extensively used in connection with automatic trip mechanisms onmachine tools. The trigger $6 in moving from the position shown in Fig.2 to that shown in Fig. 3 is arranged to break the motor circuit, and isautomatically locked in open circuit position by means of a springpressed latch 98. The switch 97 is suitably supported by means of abracket 99 on the side of the housing l9 and has a conduit I90 extendingtherefrom containing the wires forming part of the motor circuit. Theswitch 9? is in series with the magnetic switch that is directlyconnected with the motor and a pressure control switch and stacktemperature or low water cut-out switch associated with the boiler incon- 1 nection with which the stoker is used. Thus, the pressure switchautomatically breaks the motor circuit to stop the stoker when the steampressure has been raised to a predetermined point and the switch 9?comes into play to break the motor circuit only in the event of anoverload on the stoker. The throwing out of operation of the motor theinstant an overload occurs suflicient to disconnect the stoker feedscrew from the transmission is of advantage naturally from thestandpoint of economy but also from the standpoint of letting theoperator know when the stoker requires attention. Obviously, when thepin 85 shears off the thing that has caused that to occur must beremedied and then the cap 93 is removed and the shear pin replaced,after which the latch 58 can be released to throw the, motor back intooperation. 9

Referring to Fig. 6, which is a wiring diagram, the relationship of theswitch 97 to the magnetic switch It)! of the motor is apparent at aglance; it is connected in series with the magnetic coil i 92 of themagnetic switch so that when an overload occurs and the switch 9'! isopened, the circuit through the coil m2 is broken and the magneticswitch I511 is thrown open and the motor stops. Mercoid switches areshown at I03 and HM also in series with the coil H32. N13 is thepressure control. switch which breaks the motor circuit when the steampressure has been raised to a predetermined point. The switch I04 can beeither a stack temperature or water cut-out switch, but is shown as ofthe former type. closed to start the motor H, the switch IM is closed byreason of the energization of coil 32 and the motor is thrown intooperation, and it is thereafter dependent for its continued operation onthe switches 9?, Hi3 and HM. Obviously, if an overload command theswitch 97 is opened. it is important that the operators attention becalled to it immediately. For that reason, a shunt connection H5 is madeacross the switch 91 for the primary winding of a transformer Mt, the,secondary winding of which is connected with an alarm m1. trated as ahell, but, ofv course, any other form of signal, such as an electric liht, could be used. The resistance through the shunt connection is suchthat there is normally no appreciable cur ever, when the switch 91 isope'ned, the only path The switch a low When the main line switch 535 isThe latter 'is herein mus-1 left forv the current is through the shuntconnection H and the alarm I01 is accordingly operated. There is,therefore, no danger of the stoker being thrown out of operation for anyprolonger period.

As a further safety feature, I provide a thermal relay B08 in serieswith the coil I02 and switch 7 91. This relay is of the well-known typewhich has a spring I09 normally tending to open the same when a mass offusible metal H9 is heated to a predetermined temperature for fusion.The heating resistance for that purpose is shown at I l I and is inseries with the motor. If the motor armature fails to turn for anyreason, as for example, in case the bearings are not lubricated, theheating of the resistance I l I will cause fusion of the metal I it] andthe relay I88 will be thrown open under the action of spring I89. Assoon as that occurs, the electric current flowing through the shuntconnection I 15 will cause the alarm [ill to be operated, and attentionwill be called immediately to the fault so that it can be remedied andthe stoker thrown back into operation with minimum delay.

It is believed the foregoing description conveys a good understanding ofall of the objects and advantages of my invention. The appended claimshave been drawn so as to cover all legitimate modifications andadaptations.

I claim:

1. In a stoker drive transmission of the type comprising a driven membersuch as a feed screw, an electric motor for driving the same, reductiongearing between the motor and the driven member for driving the latterfrom the former at a reduced speed, and a switch in the motor circuit,an overload release mechanism for disconnecting the driven member fromoperative relation to the motor and stopping the motor, said mechanismcomprising a shear pin for interconnecting two interfitting driving anddriven members of said transmission, such as a shaft and hub, said pinbeing arranged to shear off in the event of a predetermined excessiveresistance to turning of the driven member and thus permit relativerotation between the shaft and hub, said shaft and hub having V-shapednotches provided therein held in register when the pin is intact, aplate having a V-shaped projection thereon fitting in said notches;spring means normally holding said plate in such position, said platebeing movable outwardly by cam action of the projection in said notchesin the event of relative rotation between the hub and shaft, and meansoperable upon outward movement of said plate to operate the switch tobreak the motor circuit.

2. An overload release mechanism adapted to be used with a shaft and amember mounted on the shaft and having a hub portion, one of the latterelements being the driver and the other the driven element, said releasemechanism comprising a shear pin extending transversely through theshaft and hub portion to interconnect the same for drive purposes, saidpin being arranged to shear off in the event of excessive resistance toturning of the driven element, said shaft and hub having transverseV-shaped notches provided in the end thereof normally disposed inregister, a plate abutting the end of the shaft and hub having atransverse V-shaped projection fitting in said notches, said plate beingmovable outwardly by cam action of the projection in said notches uponrelative rotation between the shaft and hub resulting from shearing ofthe pin, and means operable in outward movement of the plate foroperating a device to be operated.

3. A mechanism as set forth in claim 2 including a housing from whichthe shaft and hub project, a cap removably mounted on the housing andenclosing the projecting end of the shaft and hub, said cap beingarranged to be removed to permit replacement of the shear pin, the meansoperable by the plate extending through said cap for operation of thedevice disposed outside the cover, and a coiled compression springacting between the cover and the plate for normally urging the platetoward abutment with the shaft and hub to keep the projection thereon inthe notches provided in said parts.

4. An overload release mechanism comprising a driving member, powermeans for driving said member, a driven member, a shear pin normallyconnecting said driving and driven members to rotate together, a controlmember normally disposed to turn with the driving and driven members,said control member having a V-shaped. cam projection, and one of saiddriving and driven members having a V-shaped notch normally receivingsaid projection, said control member being normally stationary withrespect to the notched member but arranged to move endwise with respectthereto by cam action of the projection in the notch upon relativerotation between the driving and driven members resulting from shearingof the shear pin, and controlling means for the power means operableupon endwise movement of said control member.

5. An overload release mechanism comprising a driving member, powermeans for driving said member, a driven member, a shear pin normallyreceived in registering diametrical holes provided in the driving anddriven members to cause said members to turn together, a control membernormally disposed to turn with the driving and driven members, saidcontrol member having a V-shaped cam projection, and one of said drivingand driven members having a V-shaped notch normally receiving saidprojection, said control member being normally stationary with respectto the notched member but arranged to move endwise with respect theretoby cam action of the projection in the notch upon relative rotationbetween the driving and driven members resulting from shearing of theshear pin, spring means for resiliently retaining the shear pin andcontrol member in their normal positions, and controlling means for thepower means operable upon endwise movement of said control member.

6. In an overload release mechanism, the combination of a first memberand a second member surrounding the first member and normally arrangedto turn therewith, a shearable pin interconnecting said members, andmeans for indicating the shearing of said pin comprising a membermounted for rotation normally with both of said members, one of saidmembers having a V-shaped notch and said third member having a V-shapedcam projection entered in said notch, whereby upon relative rotation ofsaid members resulting from shearing of the shear pin the third memberis arranged to be moved endwise by cam action of its projection in thenotch.

'7. In an overload release mechanism, the combination of a first memberand a second member surrounding the first member and normally arrangedto turn therewith, a shearable pin in terconnecting said members, meansfor indicating the shearing of said pin comprising a member mountedforrotation normally with both of said members, one of said members havinga V-shaped notch and said third member having a V-shaped cam projectionentered in said notch, whereby upon relative rotation of said membersresulting from shearing of the shear pin the third member is arranged tobe movedendwise by cam action of its projection in the notch, and springmeans for retaining the shear pin in its operative position andresisting endwise movement of the third member.

8. An overload release mechanism for a power transmission comprising incombination with a driving shaft and a driven sleeve on said shaft, a

pin, to cause endwise movement of said control member by cam action ofthe projection in its lateral movement relative to the notch, and meansoperable in endwise movement of said control member for operating adevice to be op erated. i

9. An overload release mechanism for a power transmission comprisingincombination with a driving shaft and a driven sleeve on said shaft, ashear pin connecting the shaft and sleeve to rotate together, a controlmember mounted on said shaft to turn therewith, said member having aV-shaped cam projection, said sleeve having a V-shaped notch normallyreceiving said projection, said projection being arranged in the eventof rotation of the shaft and control member relative to the sleeve,resulting from shearing of the 15 pin, to cause endwise movement of saidcontrol member by cam action of the projection in its lateral movementrelative to the notch, spring means resisting endwise movement of saidcontrol member, and means operable in endwise movement of said controlmember for operating a device to be operated. 7

- FLOYD R. NELSON.

